Tube for heat exchanger and method of manufacturing the same

ABSTRACT

A tube for a heat exchanger has a tube member and a fin inserted in the tube member. The tube member has a first wall having a first end portion and a second wall having a second end portion. The second end portion of the second wall is folded over the first end portion of the first wall. Also, an end of the fin is held between the first end portion and the second end portion of the tube member. Further, the end of the fin has a bent portion at an end of the first end portion within the folded second end portion. The bent portion of the fin is engaged with the first end portion of the tube member for positioning the fin with respect to the tube member.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2005-315213filed on Oct. 28, 2005, the disclosure of which is incorporated hereinby reference.

FIELD OF THE INVENTION

The present invention relates to tubes for a heat exchanger such as anevaporator and a method of manufacturing the same.

BACKGROUND OF THE INVENTION

In a heat exchanger, tubes have inner fins therein. The tubes having theinner fins are for example manufactured in a method described inJapanese Patent Publication No. 2003-336989. Hereafter, the tubes havingthe inner fins are referred to as inner fin tubes. In each of the innerfin tubes, a corrugated inner fin is disposed in a tube wall having aflat tubular shape.

The tube wall is for example formed by folding a band plate at a middleportion and crimping ends of the folded band plate. The tube wall has abent portion at a first end and a crimped portion at a second end in across-section defined in a direction perpendicular to a longitudinalaxis of the tube. The inner fin is formed by shaping a band plate into awave form.

The inner fin is arranged in the tube such that its first end is incontact with an inside of the bent portion of the tube wall and itssecond end is interposed between the crimped ends of the tube wall.Namely, the ends of the tube wall are crimped in a condition interposingthe second end of the inner fin between them so as to restrictdisplacement of the inner fin in the tube wall.

Since the displacement of the inner fin is reduced, the above inner fintube can be manufactured continuously at high speeds. Namely, asdisclosed in Japanese Patent Publication No. 2003-336989, the tube walland the inner fin are continuously formed and the inner fin is insertedin the tube wall in the same roll forming apparatus.

In the above inner fin tubes, however, when the ends of the folded tubewall are crimped even in a condition interposing the second end of theinner fin between them, the inner fin is likely to be displaced due toshrinkage of a corrugated portion of the inner fin. If the inner fin isdisplaced, it is difficult to stably or uniformly form a crimped end onthe tube wall. Moreover, joining portions between an inner surface ofthe tube wall and the inner fin are likely to be displaced.

SUMMARY OF THE INVENTION

The present invention is made in view of the foregoing matter, and it isan object of the present invention to provide a tube for a heatexchanger, capable of positioning a fin with respect to a tube member.

It is another object of the present invention to provide a method ofmanufacturing a tube for a heat exchanger, capable of positioning a finwith respect to a tube member.

It is further another object of the present invention to provide a tubefor a heat exchanger and a method of manufacturing the tube, capable ofcrimping ends of a tube member stably.

According to a first aspect of the present invention, a heat exchangerincludes a tube member and a fin inserted in the tube member. The tubemember has a first wall and a second wall that are opposed to eachother. The first wall has a first end portion and the second wall has asecond end portion. The second end portion is folded over the first endportion. The fin has an end held between the first end portion and thesecond end portion of the tube member. Further, the end of the fin has afin bent portion over an end of the first end portion of the tubemember. The fin bent portion contacts the end of the first end portionfor positioning the fin with respect to the tube.

In manufacturing the tube, the tube member is formed to have the firstwall and the second wall. The second end portion of the second wall isfolded after the fin is inserted in the tube member. Also, the secondend portion is folded in a condition that the end of the fin is heldbetween the first end portion and the second end portion and the finbent portion is engaged with the first end portion. For example, the finbent portion can be formed before the second end portion of the tubemember is folded. Alternatively, the fin bent portion can be formed whenthe second end portion of the tube member is folded.

Since the fin is positioned with respect to the tube member by the finbent portion, the second end portion of the tube member is stably oruniformly folded over the first end portion and the end of the fin. Assuch, the first end portion and the second end portion of the tubemember are stably or uniformly crimped.

Accordingly, a plurality of tubes can be uniformly formed. In a heatexchanger having the tubes, a clearance is uniformly defined between anend of each tube and a tube hole of a header tank. Therefore, thequality of joining between the tubes and the header tank improves.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome more apparent from the following detailed description made withreference to the accompanying drawings, in which like parts aredesignated by like reference numbers and in which:

FIG. 1 is a cross-sectional view of an inner fin tube taken in adirection perpendicular to a longitudinal axis of the inner fin tubeaccording to a first embodiment of the present invention;

FIG. 2 is an enlarged view of the inner fin tube at a part denoted by acircle II in FIG. 1;

FIG. 3 is a schematic side view of a heat exchanger having the inner fintubes according to the first embodiment of the present invention;

FIG. 4 is a schematic diagram of an apparatus of manufacturing the innerfin tubes according to the first embodiment of the present invention;

FIG. 5 is an explanatory view for showing a crimping step performed bythe apparatus according to the first embodiment of the presentinvention;

FIG. 6 is a schematic sectional view of an inner fin tube in a crimpingstep of an inner fin tube manufacturing method according to a secondembodiment of the present invention; and

FIG. 7 is a schematic sectional view of the inner fin tube in anotherstage of the crimping step according to the second embodiment of thepresent invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT First Embodiment

A first embodiment of the present invention will be described withreference to FIGS. 1 through 5. As shown in FIG. 1, an inner fin tube 10of the first embodiment has a tube member 11 and an inner fin 12inserted in the tube member 11. As shown in FIG. 3, the inner fin tube10 is for example used as a tube of a heat exchanger 20 such as anevaporator of a refrigerating cycle.

The tube member 11 has a flat tubular shape. The tube member 11 isformed by folding a thin aluminum band plate. As shown in FIG. 1, in across-section defined in a direction perpendicular to a longitudinaldirection of the tube member 11, the tube member 11 has a substantiallyelliptical shape. In FIG. 1, an arrow A1 denotes a direction parallel toa major axis of the elliptical shape.

The band plate is folded at a substantially middle portion thereof sothat the tube member 11 has flat plate portions 11 b and a bent portion11 a at ends of the flat plate portions 11 b. The bent portion 11 a hasan arc shape, for example. Also, the bent portion 11 a has a shapecorresponding to a part of a circle that has a diameter equivalent to adistance between the flat plate portions 11 b of the tube member 11.Alternatively, the bent portion 11 a has another shape such as a V-shapeor a bracket-shape.

The flat plate portions 11 b extend from the bent potion 11 a. As shownin FIG. 2, the flat plate portions 11 b have inclined wall portions 11 c3, 11 c 4 at ends opposite to the bent portion 11 a. The inclined wallportions 11 c 3, 11 c 4 are inclined toward a centerline between theflat plate portions 11 b to form a V-shape. Further, the flat plateportions 11 b have a first end portion 11 c and a second end portion 11c 2 at the ends of the inclined wall portions 11 c 3, 11 c 4,respectively. The first end portion 11 c 1 and the second end 11 c 2 arecrimped.

For example, the second end portion 11 c 2 overlaps and is folded overthe first end portion 11 c 1. Specifically, the second end portion 11 c2 has a length equal to or larger than twice of the first end portion 11c 1. The second end portion 11 c 2 has a first portion extending fromthe end of the inclined wall portion 11 c 4 parallel to and opposed toan inner surface of the first end portion 11 c 1, a second portionextending from the first portion and wrapped over the end of the firstend portion 11 c 1, and a third portion extending from the secondportion along an outer wall of the first end portion 11 c 1. The thirdportion ends at a position adjacent to a boundary between the first endportion 11 c 1 and the inclined wall portion 11 c 3.

As such, a crimped portion 11 c is formed at an end opposite to the bentportion 11 a by crimping the ends of the flat plate portions 11 b, i.e.,by folding the second end portion 11 c 2 over the first end portion 11c. Here, crimping means a structure that the first end portion 11 c 1and the second end portion 11 c 2 are closed by folding the second endportion 11 c 2 over the first end portion 11 c 1.

As shown in FIGS. 1 and 2, the second end portion 11 c 2 is folded andwrapped over the first end portion 11 c 1 such that both surfaces of thefirst end portion 11 c 1 are generally included in the folded second endportion 11 c 2. In this embodiment, the crimped portion 11 c has agenerally flat shape. The crimped portion 11 c extends from the inclinedwall portions 11 c 3, 11 c 4 in a length substantially equal to thedistance between the flat plate portions 11 b.

The inner fin 12 is used for providing a turbulence effect of a fluidflowing in the tube member 11 and increasing a heat transfer area. Theinner fin 12 is formed of a thin aluminum band plate that is thinnerthan the band plate of the tube member 11 by roll forming. Also, theinner fin 12 is formed with corrugated portion 12 a having a wave form.

Further, the inner fin 12 has a first flat plate portion 12 b and asecond flat plate portion 12 c at ends with respect to a width of theband plate. The inner fin 12 is inserted in the tube member 11 such thatthe first flat portion 12 b is in contact with an inner wall of the bentportion 11 a of the tube member 11. Further, the first end portion 11 c1 and the second end portion 11 c 2 of the tube member 11 are crimped ina condition that the second flat portion 12 c is interposed between thefirst end portion 11 c 1 and the second end portion 11 c 2.

Further, the second flat portion 12 c is formed with a bent portion 12 c1. The bent portion 12 c 1 is formed by bending an end of the secondflat portion 12 c into a substantially L-shape. The bent portion 12 c 1contacts and partly covers the end of the first end portion 11 c 1 ofthe tube member 11. The bent portion 12 c 1 extends parallel to an endsurface of the first end portion 11 c 1. As such, the bent portion 12 c1 provides a hook portion to be engaged with or held on the end of thefirst end portion 11 c 1.

The bent portion 12 c 1 determines a position of the inner fin 12 withrespect to the tube member 11 against a force generated in the inner fin12 to move into the inside of the tube member 11 before a brazing step.Namely, the bent portion 12 c 1 serves as a positioning member toposition the inner fin 12 with respect to the tube member 11.

The bent portion 12 c 1 has the length in a direction perpendicular tothe first end portion 11 c 1 equal to or less than the thickness of thefirst end portion 11 c 1. Preferably, the bent portion 12 c 1 has thelength as long as possible within the thickness of the first end portion11 c 1. The bent portion 12 c 1 can be formed throughout the end of thesecond flat plate portion 12 c in a longitudinal direction of the innerfin 12. Alternatively, the bent portion 12 c 1 can be formed partly orat intervals in the longitudinal direction of the inner fin 12.

The inner fin tubes 10 having the above configuration are stacked atpredetermined intervals, as shown in FIG. 3. Further, outer fins 21 areinterposed between the inner fin tubes 10. Each of the outer fins 21have a corrugated shape, similar to the inner fins 12. Thus, the stackof the inner fin tubes 10 and the outer fins 21 forms a core portion 22for performing heat exchange between an inner fluid and an outer fluid.Further, longitudinal ends of the inner fin tubes 10 are coupled to afirst header tank 23 and a second header tank 24. As such, the heatexchanger 20 is constructed.

Each of the first header tank 23 and the second header tank 24 is formedwith tube holes 23 a (double-dashed chain line in FIG. 2). Thelongitudinal ends of the inner fin tubes 10 are inserted in the tubeholes 23 a and joined to the first header tank 23 and the second headertank 24 by brazing.

The first header tank 23 and the second header tank 24 are provided witha fluid inlet member 25 and a fluid outlet member 26, respectively. Whenthe heat exchanger 20 shown in FIG. 3 is used as the evaporator, arefrigerant as an inner fluid circulating in the refrigerating cycleflows into the first header tank 23 through the fluid inlet member 25.Further, the refrigerant flows through the inner fin tubes 10 toward thesecond header tank 24. Then, the refrigerant flows out from the fluidoutlet port 26. Heat exchange is performed between the refrigerantflowing in the inner fin tubes 10 and air flowing outside of the coreportion 22. As such, while the refrigerant evaporates, the air iscooled. The air is for example used for air conditioning.

Next, a method of manufacturing the above inner fin tubes 10 will bedescribed with reference to FIGS. 4 and 5. FIG. 4 shows a manufacturingapparatus 100 for manufacturing the inner fin tubes 10.

The manufacturing apparatus 100 has a tube forming unit 110 for formingthe tube member 11 and inserting the inner fin 12 in the tube member 11,an inner fin forming unit 120 for forming the inner fin 12, an inner fincarrying unit 130 for carrying the inner fin 12 to the tube forming unit110, and the like.

Further, the tube forming unit 110 has a tube outer wall forming section110A, an inserting and crimping section 110B and a cutting section 110C.The sections 110A to 110C are arranged in series. The tube outer wall 11is formed by using a coiled band plate material. Although notillustrated, rollers are arranged between the respective sections 110Ato 110C for carrying the material, for example. Thus, operations in therespective sections 110A to 110C can be performed continuously.

The tube outer wall forming section 110A has multiple rollers for mainlyforming the bent portion 11 a and the flat plate portions 11 b from thecoiled band plate material, thereby to form a tube outer wall as thetube member 11. The inserting and crimping section 110B has multiplerollers R0 through Rn for forming the crimped portion 11 c on the tubeouter wall 11 after inserting the inner fin 12 in the tube outer wall11. In the cutting section 110C, the continuous formed member carriedfrom the inserting and crimping section 110B is cut into a predeterminedlength, thereby producing the individual inner fin tubes 10.

FIG. 5 shows a crimping step performed in the inserting and crimpingsection 110B. In the inserting and crimping section 110B, the rollers R0to Rn are arranged in a processing direction, i.e., a feeding direction.Further, each of the rollers R0 to Rn rotates while contacting thesecond end portion 11 c of the tube outer wall 11.

Moreover, the rollers R0 to Rn are arranged such that directions ofrotation axes of the rollers R0 to Rn varies from a position A0 to aposition An, as shown in FIG. 5. That is, a rotation axis A0 of theroller R0 is parallel to an original extending direction of the secondend portion 11 c 2. A rotation axis An of the roller Rn is parallel tothe rotation axis A0 of the roller R0. Rollers between the roller R0 andthe roller Rn are arranged such that the rotation axes thereof aregradually angled from the rotation axis A0 to the rotation axis An.

Thus, the rotation axes are varied 180 degrees from the rotation axis A0to the rotation axis An. As such, the second end portion 11 c 2, whichis straight before the folding, is folded over the first end portion 11c 1 through the rollers R0 to Rn. Accordingly, the crimped portion 11 cis formed.

The inner fin forming unit 120 is arranged parallel to the tube outerwall forming section 110A such that the formed inner fin 12 is locatedseparate from the tube outer wall 11 formed in the tube outer wallforming section 110A by a predetermined distance in a horizontaldirection and under the tube outer wall 11. The inner fin 12 is formedby using a coiled band plate material. In the inner fin forming unit120, the corrugated portion 12 a, the first and second flat portions 12b, 12 c and the L-shaped bent portion 12 c 1 are formed on the bandplate material buying rollers. As such, a continuous inner fin 12 in aform of longitudinal band is formed.

The inner fin carrying unit 130 feeds the continuous inner fin 12 fromthe inner fin forming unit 120 to the inserting and crimping section110B.

In the above manufacturing apparatus 100, first, the tube outer wall 11is formed from the band plate material in the tube outer wall formingsection 110A (tube outer wall forming step). Also, in the inner finforming unit 120, the continuous inner fin 12 is formed. The continuousinner fin 12 is carried to the inserting and crimping section 110B bythe inner fin carrying unit 130.

Next, in the inserting and crimping section 110B, the continuous innerfin 12 is inserted in the continuous tube outer wall 11 (insertingstep). Then, the second end portion 11 c 2 of the tube outer wall 11 iscontinuously folded over the first end portion 11 c 1 (crimping sep).Thus, a continuous inner fin tube is formed.

In the inserting step, the bent portion 12 c 1 of the inner fin 12engages with the end of the first end portion 11 c 1 of the tube outerwall 11. Namely, the inner fin 12 is positioned with respect to the tubeouter wall 11 by the bent portion 12 c 1. Then, in the crimping step,the second end portion 11 c 2 of the tube outer wall 11 is sequentiallyfolded over the first end portion 11 c 1 by the rollers R0 to Rn in acondition that the second flat portion 12 c of the continuous inner fin12 is sandwiched between the first end portion 11 c 1 and the second endportion 11 c 2 and the bent portion 12 c 1 is engaged with the first endportion 11 c 1. Accordingly, even after the crimping step, the bentportion 12 c 1 maintains the condition engaged with the first endportion 11 c 1.

Thereafter, the continuous inner fin tube 10 is cut into a predeterminedlength. The cut inner fin tubes 10 are arranged regularly and in apredetermined area (110D). Accordingly, the individual inner fin tubes10 for the heat exchanger 20 are produced.

In the inserting step and the crimping step, the bent portion 12 c 1 isheld in contact with the end of the first end portion 11 c 1. Namely,the inner fin 12 is positioned with respect to the tube outer wall 11 bythe bent portion 12 c 1. As such, it is less likely that the inner fin12 will be displaced with respect to the tube outer wall 11. Therefore,in the crimping step, the bending position of the second end portion 11c 2 is stabled or uniformed. Namely, the second end portion 11 c 2 isuniformly folded over the first end portion 11 c 1. Accordingly, theinner fin tubes 10, the ends of which are uniformly crimped, aremanufactured.

Further, in the crimping step, the second end portion 11 c 2 is bendover a corner of the bent portion 12 c 1 of the inner fin 12. Thus, thesecond end potion 11 c 2 is turned substantially 180 degrees over thebent portion 12 c 1 while maintaining a bent shape (R-shape). Moreover,the second end portion 11 c 2 can uniformly maintain a predeterminedlength L at a folded end, as shown in FIG. 2.

Since the crimped portion 11 c is uniformly formed, the inner fin tubes10 have uniformed outlines. Thus, in constructing the heat exchanger 20using the above inner fin tubes 10, clearances are substantially equallydefined between the tube holes 23 a of the first and second header tanks23, 24 and the ends of the plural inner fin tubes 10. Therefore, theinner fin tubes 10 and the first and second header tanks 23, 24 aresecurely jointed to each other.

Specifically, since the inner fin tubes 10 have the folded ends of thesecond end portions 11 c 2 in the substantially equal length L, theclearance S defined between each tube hole 23 a and each inner fin tube10 can be reduced. Namely, unevenness of the clearances among the innerfin tubes 10 is reduced. Therefore, a quality of brazing improves.

Accordingly, the inner fin tubes 10 are securely brazed to the first andsecond header tanks 23, 24. It is less likely that the inner fluid suchas the refrigerant will leak through the joining portions between theinner fin tubes 10 and the tube holes 23 a of the first and secondheader tanks 23, 24. As such, reliability of the heat exchanger 20improves.

In the above tube member 11, the flat plate portions 11 b are continuousthrough the bent portion (connecting portion) 11 a on a side opposite tothe crimped end 11 c. Therefore, durability of the inner fin tube 10against a pressure of the inner fluid improves.

Also, the length of the bent portion 12 c 1 of the inner fin 12 isshorter than the thickness of the end of the first end portion 11 c 1.Therefore, it is less likely that the bent portion 12 c 1 will interferewith the folded second end portion 11 c 2.

Second Embodiment

Next, a second embodiment of the present invention will be describedwith reference to FIGS. 6 and 7. In the second embodiment, inner fintubes 10 have the same shape as the inner-fin tubes 10 of the firstembodiment shown in FIG. 1. However, a method of manufacturing the innerfin tubes 10 is different from that of the first embodiment. FIG. 6shows an early stage of the crimping step for crimping the first endportion 11 c and the second end portion 11 c 2. FIG. 7 shows anintermediate stage of the crimping step.

In the second embodiment, the bent portion 12 c 1 of the inner fin 12 isformed at the same time as folding the second end portion 12 c 1 in thecrimping step. In other words, the bent portion 12 c 1 is not formed inthe inner fin forming unit 120.

In a condition that the inner fin 12 is inserted in the tube outer wall11 in the inserting step, the second flat plate portion 12 c is heldbetween the first end portion 11 c 1 and the second end portion 11 c 2,and the end of the second flat plate portion 12 c extends longer thanthe first end portion 11 c 1, as shown in FIG. 6. It is preferable thatthe end of the second flat plate portion 12 c protrudes from the end ofthe first end portion 11 c 1 as long as possible in a range shorter thanthe thickness of the first end portion 11 c 1.

When the second end portion 11 c 2 is bent in the crimping step, the endof the second flat plate portion 12 c of the inner fin 12 is bent withthe second end portion 11 c 2 at a position corresponding to the end ofthe first end portion 11 c 1 as a bending base point, as shown in FIG.7. As such, the bent portion 12 c 1 is formed in the crimping step. Alsoin this case, because the inner fin 12 is positioned with respect to thetube outer wall 11 by the bent portion 12 c 1, it is less likely thatthe inner fin 12 will be displaced with respect to the tube outer wall11 in the crimping step. Accordingly, the crimped portion 11 c is stablyand uniformly formed.

Also in this embodiment, the flat plate portions 11 b are continuousthrough the bent portion (connecting portion) 11 a on a side opposite tothe crimped end 11 c. Therefore, durability of the inner fin tube 10against a pressure of the inner fluid improves. Also, the length of thebent portion 12 c 1 of the inner fin 12 is shorter than the thickness ofthe end of the first end portion 11 c 1. Therefore, it is less likelythat the bent portion 12 c 1 will interfere with the folded second endportion 11 c 2.

The use of the inner fin tubes 10 of the first and second embodimentwill not be limited to the evaporator. For example, the inner fin tubes10 can be used in other heat exchangers such as a radiator, a condenserand a heater core.

Also, the shape of the inner fin 12 is not limited to the corrugatedshape having the corrugated portion 12 a. For example, the inner fin 12have projections and grooves discontinuously or irregularly.Alternatively, the inner fin 12 is formed with openings and the like.

In the above embodiments, the flat plate portions 11 b of the tubemember 11 are continuous through the bent portion 11 a. However, theshape of the tube member 11 is not limited to the above. For example,the flat plate portions 11 b can be crimped at both ends.

The example embodiments of the present invention are described above.However, the present invention is not limited to the above exampleembodiments, but may be implemented in other ways without departing fromthe spirit of the invention.

1. A tube for a heat exchanger, comprising: a tube member having a firstwall and a second wall that are opposed to each other, the first wallhaving a first end portion, the second wall having a second end portion,the second end portion folded over the first end portion; and a findisposed in the tube member, the fin having an end held between thefirst end portion and the second end portion of the tube member, whereinthe end of the fin has a fin bent portion over an end of the first endportion of the tube member for positioning the fin with respect to thetube member.
 2. The tube according to claim 1, wherein the first wallconnects to the second wall through a tube bent portion on a sideopposite to the first end portion and the second end portion.
 3. Thetube according to claim 1, wherein the fin bent portion has a dimensionwith respect to a direction perpendicular to the first end portion ofthe tube member equal to or smaller than a thickness of the first endportion.
 4. The tube according to claim 1, wherein the fin bent portionhas a substantially L-shape.
 5. A heat exchanger comprising a tubeaccording to claim
 1. 6. The heat exchanger according to claim 5,further comprising: a header tank formed with a plurality of tube holes,wherein the tube is one of a plurality of tubes and ends of the tubesare received in the tube holes of the header tank.
 7. A method ofmanufacturing a tube for a heat exchanger, comprising: forming a tubemember to have a first wall having a first end portion and a second wallhaving a second end portion; inserting a fin between the first wall andthe second wall of the tube member; folding the second end portion ofthe second wall over the first end portion of the first wall in acondition that an end of the fin is interposed between the first endportion and the second end portion and the end of the fin is engagedwith the first end portion of the first wall by a fin bent portion. 8.The method according to claim 7, further comprising: forming the finbent portion on the end of the fin before the inserting.
 9. The methodaccording to claim 7, wherein the folding includes bending the end ofthe fin over an end of the first end portion of the tube member to formthe fin bent portion.
 10. The method according to claim 9, wherein theinserting includes placing the fin such that the end of the finprotrudes from the first end portion of the tube member.
 11. The methodaccording to claim 7, further comprising: cutting the tube member into apredetermined length after the folding.
 12. The method according toclaim 7, wherein the forming of the tube member includes folding a platemember to have the first wall, the second wall and a tube bent portionbetween the first wall and the second wall.